Early European Farmers displaced the mesolithic Hunter Gatherers in the areas they both inhabited but there wasn't a complete elimination of the HG groups. In fact, the I1 Y haplogroup associated with Germanic tribes comes from the mesolithic Hunter Gatherers, so they obviously were _not_ totally eliminated. Actually, it was the EEF group that was more or less fully eliminated in Scandinavia when the Yamnaya appeared because both groups exploited similar areas. They wanted loess soils along rivers, while the Hunter Gatherers lived near the coastline.